IN VIVO HALF LIFE INCREASED FUSION PROTEIN OR PEPTIDE MAINTAINED BY SUSTAINED IN VIVO RELEASE, AND METHOD FOR INCREASNG IN VIVO HALF-LIFE USING SAME - The present invention relates to a fusion protein or peptide, the in vivo half-life of which is increased by maintaining in vivo sustained release, and to a method for increasing in vivo half-life using same. A fusion protein or peptide according to the present invention has excellent in vivo stability by binding a physiologically active protein or physiologically active peptide to an alpha-1 antitrypsin or alpha-1 antitrypsin mutant with one or more amino acids mutated to maintain the in vivo sustained release and to significantly increase the half-life thereof in blood (T1/2) compared to an inherent physiologically active protein or physiologically active peptide. Thus, a fusion protein or peptide according to the present invention can be useful in developing a sustained-release preparation of a protein or peptide drug.